An arrangement for teeming molten aluminum-containing material in a continuous casting apparatus generally includes a tundish, a casting nozzle which is mounted on the tundish and a stopper rod for regulating the flow of molten material through the casting nozzle. The arrangement can also include a control system for controlling the depth of penetration of the stopper rod into the casting nozzle within predetermined limits.
Regulation of the flow of molten material using nozzles and stopper rods is disclosed in various publications. For example, the Deutschen Gesellschaft fur Metallkunde e.V. organized a symposium entitled "Stranggiessen-Schmelzen-Giessen-Uberwachen" (Continuous Casting-Melting-Casting-Monitoring) in which bath level regulation using the eddy principle was discussed. The lectures presented at the symposium were published in 1986 and page 331 of the text illustrates a control system containing a nozzle and a stopper rod. The nozzle is fixed to the bottom of a tundish and the lower end of the nozzle projects into a mold.
Under certain circumstances, the flow velocity of the aluminum-containing melt through the casting nozzle can change with a resultant change in the static pressure. When the flow velocity of the melt is very high, a relatively large subatmospheric pressure is generated an the nozzle inlet or outlet. Oxide and dirt particles from the surface of the bath in the tundish and/or from the surface of the pool in the mold are then sucked into the melt and adversely affect the quality of the continuously cast billet or strand.